Its not about punishing or taking away a currency its about rUK not wanting to be financially responsible for a independent scotland. If there was currency union then the rUK would have to bail out iScotland if /when it get into trouble.
If you want the stability and protection of the pound then you need to remain part of the union.
Sometimes I hate this bloody website.. Just spent about an hour writing a reply only to lose it all due to time out..
Either way - huge financial risk is involved. If Scotland proves it can stand on it's own two feet the long term effect of not having a currency union would be much more costly and damaging.
In the short term it certainly appears to be presented to us as a punishment/consequence. I would like to think Scotland has the benefit to any doubt in it's ability to thrive - given the opportunity and power to do so. I believe what can be good for Scotland can also be good for the rest of the UK, and it's not necessarily about breaking up the union but how we can operate individually to give everyone the best deal.